title: Comparative mutagenicities of N6-methoxy-2,6-diaminopurine and N6-methoxyaminopurine 2'-deoxyribonucleosides and their 5'-triphosphates.
abstract: The structure of the deoxyribonucleoside derived from N 6-methoxy-2, 6-diaminopurine (dK) was examined by NMR. The methoxyamino residue was found predominantly in the imino rather than the amino tautomer (ratio: 9:1 in DMSO). The nucleoside proved to be a potent transition mutagen in Escherichia coli , in contrast to the closely related nucleoside derived from the analogue N6-methoxyaminopurine (dZ), which was only weakly mutagenic. The 5'-triphosphate derivatives, dKTP and dZTP, were synthesized; Taq polymerase incorporated dKTP opposite both T and, less well, opposite dC in template DNA. Both analogue triphosphates produced transition mutations when added to PCR reactions. In each case, there was a large excess of AT-->GC compared to GC-->AT mutations (ratios were 15:1 for dKTP and 10:1 for dZTP). Polymerase extension times in each cycle had to be extended, consistent with a decreased rate of DNA synthesis in the presence of the analogues. This and the mutagenic ratios are discussed in terms of syn-anti inversion of the methoxyl group.
authors.affiliation: Medical Research Council, Laboratory of Molecular Biology and Centre for Protein Engineering, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: F
authors.initials: F
authors.lastname: Hill
authors.forename: D M
authors.initials: DM
authors.lastname: Williams
authors.forename: D
authors.initials: D
authors.lastname: Loakes
authors.forename: D M
authors.initials: DM
authors.lastname: Brown
mesh_terms: D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000633:toxicity; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics; D003853:Deoxyribonucleosides / Q000737:chemistry / Q000633:toxicity*; D003854:Deoxyribonucleotides / Q000737:chemistry / Q000633:toxicity*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D003853:Deoxyribonucleosides; D003854:Deoxyribonucleotides; D009153:Mutagens; C066661:5-amino-1-(2'-deoxy-beta-ribofuranosyl)imidazole-4-carboxamide-5'-triphosphate; D000620:Aminoimidazole Carboxamide; C066662:5-amino-1-(2'-deoxy-beta-D-ribofuranosyl)imidazole-4-carboxamide; D004247:DNA